Gas analyzer

ABSTRACT

An improved gas analyzer for analyzing the concentrations and amounts of one or more different gases in drilling mud returning from a borehole is disclosed. An oil well drilling rig re-circulates the drilling mud by continuously pumping it through a gas separation means. The gas separation means generally includes a fluid stop, a bubble jar and a dririte chamber in order to separate the gases from the drilling mud. A gas sample from these separated gases can be mixed with a carrier gas and are conveyed to gas analyzing means where the concentration of the different hydrocarbon components of the gases in the mud can be continuously measured.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 12/514,951 entitled “Gas Analyzer,” which was filed on May 14,2009 now U.S. Pat. No. 8,171,772, and which is the U.S. national phaseapplication of International Application No. PCT/US08/79722, filed onOct. 13, 2008 under the PCT (Patent Cooperation Treaty), whichdesignated the US and claims priority to U.S. Provisional PatentApplication No. 60/981,873, filed Oct. 23, 2007. The entire contents ofthese applications are incorporated herein by reference.

TECHNICAL FIELD

Embodiments are generally related to drilling and/or environmentaloperations. Embodiments are additionally related to well loggingtechniques utilized during drilling operations. Embodiments are alsorelated to methods and systems for analyzing the concentration andamount of gas produced from mud during drilling of an oil well.

BACKGROUND OF THE INVENTION

In oil well drilling operations, a drill bit can be mounted on the endof an elongated rotating drill string which turns the bit and causes itto cut away the underlying earth and rock formations. During thisoperation, a drilling mud is continuously pumped down through the drillstring and into the region around the drill bit and then back up to thesurface. This drilling mud is typically made up of clays, chemicaladditives and/or an oil or water base and performs two importantfunctions. First, the drilling mud acts as a coolant and lubricates thedrill bit during operation and it collects the drill cuttings andcarries them back to the surface of the well. Second, the drilling mudalso serves to maintain a hydrostatic pressure, which preventspressurized gases from the earth from blowing out through the drilledwell. In addition, the mud may pick up and entrain gases present in thebottom of the well and deliver them to the surface along with the drillcuttings.

Drilling mud generally constitutes a liquid carrier, typically water ordiesel oil, which is mixed with additives. In the case of a water-basedmud, this may include bentonite day and various chemicals. The mudcarries out several functions for assisting in the drilling process,including carrying away cuttings and fine solids produced by the drillbit as it bores through the rock. Entrained solids raise the mud'sdensity and viscosity, leading to many drilling problems, including areduced rate of penetration, loss of mud downhole and filter cakebuildup. The portion of the drilling mud being returned from the wellwhich includes various gaseous components to be analyzed must beseparated from the mud.

It has been common in the past to provide a log of the drillingoperation that will permit the nature of the earth formation throughwhich the drill bit is penetrating. The log enables the drillingoperator to ascertain the presence of oil or gas in the formation beingdrilled and also the location of such oil or gas in the well. As part ofthis logging operation, samples of the drill cuttings from predetermineddepths of the well are collected and analyzed. Generally, these samplescan be collected to represent a desired interval of drilling, such asevery ten feet of well drilled or every thirty feet drilled.

In a majority of prior art mud logging systems, the information recordedfrom the drilling mud reaching the surface of the well, is generallydone on a manual basis. All of the measurements and the measuringequipment require constant supervision so a logging operation generallyinvolves two mud loggers each working alternate twelve-hour shifts. Thewell mud logging techniques have also made use of gas chromatography toascertain the presence of different hydrocarbon species in the mud beingreturned. The gas chromatography technique involves taking samples ofgas from the drilling mud and passing that gas through special columnsfilled with materials that allow different gases to flow at differentrates. A further disadvantage of the prior art chromatographic gasanalysis technique results from the fact that it is not possible toseparate all of the hydrocarbon gas from the returning mud and thereforeit is not possible with chromatographic analysis to ascertain the actualconcentration of any species in the mud.

Based on the foregoing it is believed that a need exists for an improvedsystem and method for analyzing the concentrations and amounts of one ormore different gases from the mud produced by drilling an oil well.

BRIEF SUMMARY

The following summary is provided to facilitate an understanding of someof the innovative features unique to the embodiments disclosed and isnot intended to be a full description. A full appreciation of thevarious aspects of the embodiments can be gained by taking the entirespecification, claims, drawings, and abstract as a whole.

It is, therefore, one aspect of the present invention to provide forimproved well logging during drilling.

It is another aspect of the present invention to provide for improvedsystem and method for analyzing the concentrations and amounts of one ormore different gases in drilling mud returning from the borehole.

The aforementioned aspects and other objectives and advantages can nowbe achieved as described herein. An improved gas analyzer for analyzingthe concentrations and amounts of one or more different gases indrilling mud returning from a borehole is disclosed. An oil welldrilling rig re-circulates the drilling mud by continuously pumping itthrough a gas separation means. The gas separation means generallyincludes a fluid stop, a bubble jar and a dririte chamber in order toseparate various gaseous components from the drilling mud. A gas samplefrom these separated gases can be mixed with a carrier gas and areconveyed to gas analyzing means where the concentration of the differenthydrocarbon components of the gases in the mud are continuouslymeasured.

The carrier air can be passed through a silica gel scrubber and to apump (e.g., Thomas pump), thereby maintaining the flow of the carrierair within predetermined parameters. The sample gas from the driritechamber along with the carrier air is subjected to analysis in gasanalyzing means to produce a component gas signal whose valuecorresponds to the concentration of the component in the gas mixture.The carrier air is simultaneously flowed at a rate such that the volumeof carrier air is at least several times greater than the volume of thesample gas in the drilling mud.

The sample gas is continuously subjected to different analysis in thegas analyzing means to produce different gaseous component concentrationsignals whose values at any instant represent, respectively, theconcentrations at that instant of the different gaseous components inthe separated gas. These different gaseous component concentrationsignals are processed continuously in signal processing means to providea continuous logging signal and thus provides an indication of theinstantaneous concentration of the different gaseous components in thedrilling mud.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, in which like reference numerals refer toidentical or functionally-similar elements throughout the separate viewsand which are incorporated in and form a part of the specification,further illustrate the embodiments and, together with the de aileddescription, serve to explain the embodiments disclosed herein.

FIG. 1 illustrates a block diagram showing the major components of a mudanalysis system, in accordance with a preferred embodiment;

FIG. 2 illustrates a schematic representation of a gas separation meansfor separating gases from the drilling mud, in accordance with apreferred embodiment; and

FIG. 3 illustrates a schematic representation of a gas analyzing meansfor analyzing the gaseous components in the gas separated from thedrilling mud, in accordance with a preferred embodiment.

DETAILED DESCRIPTION

The particular values and configurations discussed in these non-limitingexamples can be varied and are cited merely to illustrate at least oneembodiment and are not intended to limit the scope thereof.

Referring to FIG. 1 a block diagram showing the major components of amud analysis system 100 is illustrated, in accordance with a preferredembodiment. The drilling mud analysis system 100 includes a gasseparation means 120, a gas analyzing means 170 and a monitoring unit195. The drilling mud 110 passes through the gas separation means 120whereby the gas which includes various gaseous components to be analyzedcan be separated from the drilling mud 110. The sample gas 130 extractedfrom the drilling mud 110 can be directed to the gas analyzing means 170where the sample gas 130 can be analyzed to ascertain their constituentparts and where other measurements are made. A carrier air 140 from asilica gel scrubber 150 can be passed through a pump 160 (e.g., a Thomaspump) to the gas analyzing means 170. The Pump 160 can be adjusted inresponse to varying pressures and volumes of the carrier air 140 andthereby maintaining the flow of the carrier air 140 within predeterminedparameters. The outlet of the pump 160 can be connected to the gasanalyzing means 170 where various chemical and electrical tests areperformed on the sample gas 130.

Atmospheric air is chosen as the carrier air 140 because of its readyavailability and because it is relatively inert with respect to thehydrocarbons contained in the sample gas 130. Other gases, such asnitrogen, may be used, for example where the ambient air contains anexcess of impurities which could affect the sample gas measurements. Thesample gas 130 is evenly mixed with the carrier air 140 and the amountof each individual gas can be determined by a Chromatograph (CG)analyzer 180 and the results can be monitored utilizing the monitoringunit 195. For example, the quantity of methane, ethane, propane,isobutane, butane and pentane can each measured by the chromatographanalyzer 180. Similarly, the total gas from the sample gas 130 can beanalyzed by the Total Gas Analyzer (TGA) 175 to determine the totalamount of gases produced. The exhaust 190 from the gas analyzing means170 is then transferred to the Pump 160 which controls the flow of thegas 130 and 140 and disposing the gas via an exhaust out 185.

Referring to FIG. 2, a schematic representation of a gas separationmeans 120 for separating gases from the drilling mud 110 is illustrated,in accordance with a preferred embodiment. Note that in FIGS. 1-3,identical or similar parts or elements are generally indicated byidentical reference numerals. The drilling mud 110 is generally capturedfrom a drilling well (not shown). As stated before the process ofcapturing drilling mud 110 from the mud pit is well known in the art.The mud 110 passes through the gas separation means 120 where gasescontained in the mud 110 can be extracted. The gas separation means 120comprises an inlet line 42 connected to a fluid stop 36 wherein the mudsample gas 130 to be analyzed can be taken from the mud 110 justentering the gas separation means 120. The fluid stop 36 can be utilizedas a check flow stop, which removes any solid matter, so that drillingmud 110 does not enter the gas analyzing means 170.

Since the rate of mud flow through the well and the depth of the wellare known, it is possible to relate the mud sample analysis to thelocation in the earth to which it pertains. The outlet 37 of the fluidstop 36 is connected to a bubble jar 40. The bubble jar 40 can be filledwith ethylene glycol in order to scrub it of water. A one-liter bubblejar 40 filled with 250 milliliters of ethylene can be installed betweenthe fluid stop 36 and the outlet 41. The outlet 41 of the bubble jar 40can be attached to “Dririte” chamber 38 with an outside exhaust 44.“Dririte” is ground anhydrite, which can be treated with an indicatorthat turns from blue to pink when saturated with water wherein some willbe in its natural white state.

The carrier air 140 from the silica gel scrubber 150 can be passedthrough an inlet 34 of a pump 160. The outlet 24 of the Pump 160 isconnected to the gas analyzing means 170 thereby maintaining the flow ofthe carrier air 140 within predetermined parameters. The flow of thesample gas 130 is indicated by line 20 and the flow of carrier air 140is indicated by line 26. The carrier air 140 is simultaneously flowedthrough the gas analyzing means 170 at a rate such that the volume ofcarrier air 140 is at least several times greater than the volume of mudsample gas 130 in the drilling mud 110. The carrier air 140 can be takenfrom inside the unit in order to maintain a constant temperature.

Referring to FIG. 3 a schematic representation of a gas analyzing means170 for analyzing the gaseous components in the gas separated from thedrilling mud 110 is illustrated, in accordance with a preferredembodiment. Note that in FIGS. 1-3, identical or similar parts orelements are generally indicated by identical reference numerals. Thecarrier air 140 flows through a flow control valve 238 wherein a portionof the carrier aft 140 passes through a solenoid valve 206, whichcontrols the flow of the carrier air 140. The line 240 is connected toactivator 202 of the sample valve 224. The activator 202 will move adiaphragm which will shift a plunger in the sample valve 224 which willchange the connections of the ports. The majority of the carrier air 140passes on through a pressure regulator 230. Pressure gauge 232 can beutilized to display the pressure.

The sample valve 224 includes seven ports identified as AIR IN PORT 234,GAS IN PORT 228, LOOP PORT A, LOOP PORT B, GAS IN PORT 218, CG PORT 220and AIR IN PORT 222. The sample gas 130 can be captured at a rateanywhere from 3 standard cubic feet an hour (scfh) to 10 scfh. Normallyit will be adjusted to capture about 6 scfh. Flow rotor 204 can be setto have an output of 6 scfh to flow control valve 216 which will exhaust3 scfh. The output of the flow control valve 216 is connected to GAS INPORT 228 and to valve 214. Thus, sample gas 130 from the mud pitcirculates through the loop 226 as well as directly into the total gasanalyzer 175 as shown as filament 208 in FIG. 3. The port 222 and 218 iscoupled and the output is passed through the filament 208 and to theexhaust 190. The filament 208 actually comprises of two platinumfilaments (not shown) with a common node, which acts as a total gasdetector. One filament is sealed which acts as a reference filament. Theother is open to the flow of sample gas 130 across it when fitted intothe filament 208. The filament 208 can be configured in a Wheatstonebridge configuration.

Similarly, the output from CG port 220 is passed through a chromatograph212. The solenoid valve 206 can be controlled by a timer (not shown) sothat every 5 minutes it activates to open the solenoid valve 206 so thatline 240 is connected to activator 202 of the sample valve 224. Theactivator 202 will move a diaphragm which will shift a plunger in thesample valve 224 which will change the connections of the ports. Thepreferred form of the sample valve 224 is a plunger running through asleeve. O-rings on the plunger fit along the sleeve so that when theplunger is moved by the activator 202 that it will make the connectionsas described. It can be appreciated, however, that in accordance withother embodiments, other means can be utilized to make theseconnections. The plunger type operation is preferred because of itscompact size.

The gas within the loop 226 can be expelled through LOOP PORT A which isconnected to the CG PORT 220, when the valve 224 is switched from normalto closed position. The air 140 from AIR IN PORT 234 flows through LOOPPORT B. The air will push the accumulated gas in this path, the loop226, out through the CG PORT 220 which can take the gas through thechromatograph reader 212, a separator 242 and filament 210. Theseparator column 242 is made of copper ¼ in. O.D. copper tubing 70inches in length. It is coiled to conserve space. The column 242 ispacked with granulated diabutial phthilate, a product manufactured byKodak Chemical of Rochester N.Y. It is provided as a liquid rubber. Thepacking is placed into the copper tubing forming the separation column242.

The chromatograph 212 can show the amounts of each of the gases present.Methane comes out of the CG PORT 220 and can be measured as a pulseacross the filament bridge 210. It is followed by ethane, propane,isobutane, and normal butane in order of ascending molecular weight. Asis well known, the chromatograph 212 will measure the first gas to bereleased from the column 242 which will be the methane. After themethane is measured, the second gas to be released from the separatormay be ethane, after it is measured the next will be propane and soforth to pentane. The measurement of the amount of gases is the same inthe total gas analyzer filament 208 and the chromatograph 212. The gasesare measured by the heat units they produce as they are flowed over aheated special material.

Traditionally the material was platinum. In a preferred embodiment, thematerial for the filament can be a thermistor bead. The thermistor beadsare a product of J. J. Enterprises in Baton Rough, La. It can beappreciated, however, that in accordance with other embodiments, othermaterial can be utilized. Also in the event that there was somepossibility there can be sufficient amounts of gases to cause the totalgas analyzer 175 to go off the scale, (exceed its capacity) then it ispossible to have an air dilution stream connected from an air flow tothe flow control valve 238. An equal amount of aft is pumped into flowcontrol valve 238. Therefore diluting the sample going to the total gasanalyzer 175 to one half the otherwise calculated value. The exhaust 190from the gas analyzing means 170 is then transferred to the pump 160through the net 32 which controls the flow of the gas 130 and 140 anddisposing the gas via an outlet 28 to the exhaust out 185.

Furthermore by providing appropriate additional valves, calibration gassources and gas separation devices, it is possible to provide purgingand calibration of the gas analyzing means 170 as well as backwashing ofthe gas separation means 120 so that different tests can be performed inrapid sequence.

It will be appreciated that variations of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. A method for analyzing the concentrations and amounts of one or moredifferent gases from a drilling rig, comprising: subjecting at least oneportion of a drilling mud being returned from a well to a gas separationmeans to separate all of a gas containing a plurality of gaseouscomponent from said at least one portion of said drilling mud;continuously subjecting a sample of said gas from said gas separationmeans and a carrier air from a pump to a gas analyzing means to producesaid plurality of gaseous component concentration signal whose value atany instant corresponds to said sample gas; and thereafter redirectingsaid sample of said gas from said gas analyzing means to said pump whichcontrols the flow of said gas and disposing said gas via an exhaust out,wherein said gas separation means comprises a fluid stop to remove aplurality of solid matter entering said gas analyzing means.
 2. Themethod of claim 1 further comprising splitting a flow of said sample ofsaid gas and said carrier air in a sample valve into a TGA (Total GasAnalyzer) column and a CG (Chromatograph) column.
 3. The method of claim1 further comprising adjusting said Pump in response to varyingpressures and volumes of said carrier air from a silica gel scrubber andthereby maintaining the flow of said carrier air within predeterminedparameters.
 4. The method of claim 1 wherein said gas separation meanscomprises a bubble jar to remove water from said sample entering saidgas analyzing means.
 5. The method of claim 4 further comprisingsplitting a flow of said sample of said gas and said carrier air in asample valve into a TGA (Total Gas Analyzer) column and a CG(Chromatograph) column.
 6. The method of claim 1 wherein said gasseparation means comprises a Dryrite chamber comprising a groundanhydrite such that water vapor does not come into contact saidchromatograph column.
 7. The method of claim 2 wherein said TGA columnand said CG column comprise a filament in a Wheatstone bridgeconfiguration.